1. Field of the Invention
The present invention relates to a tilt foot mechanism for a projector.
2. Description of the Related Art
A projector is an image display device of the projection-type for displaying image by projecting image lights on a projection surface such as a screen. Accordingly, obtaining the desired image necessitates adjustment of not only the distance between the projector and the projection surface and the relative positions of the projector and projection surface, but also the angle of the projector. Feet (tilt-feet) having adjustable lengths are thus provided on the bottom surface of the projector case whereby the angle of the projector can be adjusted by modifying the lengths of the tilt feet. This angle adjustment includes both the adjustment of the angle of inclination in the vertical direction and the adjustment of the angle of inclination in the horizontal direction.
The arrangement of the above-described tilt feet can take three forms. In the first type of projector, a single tilt foot is provided at the front of the bottom of the case, and two tilt feet are provided at the rear. In this type of projector, the angle of inclination in the vertical direction is adjusted chiefly by means of the front tilt foot, and the angle of inclination in the horizontal direction is adjusted chiefly by means of the two rear tilt feet. In the second type of projector, two tilt feet are provided at the front of the case bottom, and a fixed foot (rear foot) having a fixed, nonadjustable length is provided at the rear. In this type of projector, the angle of inclination in both the vertical and horizontal directions is adjusted by means of the two tilt feet. In the third type of projector, two tilt feet are provided at the front of the bottom of the case, and two tilt feet are also provided at the rear. In this type of projector, the angle of inclination in the vertical and horizontal directions can be adjusted by means of any of the tilt feet.
FIGS. 1A and 1B show one example of a tilt foot of the prior art. FIG. 1A shows tilt foot 70 in the locked state, and FIG. 1B shows tilt foot 70 in the released state. Tilt foot 70 includes shaft 71 that projects from the bottom surface of the case and foot 72 that contacts the installation surface such as the top surface of a table. Shaft 71 passes through opening 76 of locking lever 75 that can slide back and forth. One end of compressed spring 74 is secured to any point of the case and the other end is secured to locking lever 75.
Accordingly, the restoring force F1 of spring 74 presses the inner surface (locking surface 77) of opening 76 of locking lever 75 against shaft 71, thereby locking shaft 71 (refer to FIG. 1A). However, when a control button (not shown) is pressed, a force F2 in the opposite direction of the restoring force F1 acts upon locking lever 75 by way of a release mechanism that is not shown in the figure, whereby locking lever 75 slides and locking surface 77 separates from shaft 71 (refer to FIG. 1B). As a result, the locked state of shaft 71 is released, and the length of the extension of shaft 71 can be adjusted. After the length of the extension of shaft 71 has been adjusted to the desired length, the control button is released, and locking lever 75 automatically returns to its original position, whereby shaft 71 is again locked.
FIGS. 2A and 2B show another example of a tilt foot of the prior art. FIG. 2A shows tilt foot 80 in the locked state, and FIG. 2B shows tilt foot 80 in the released state. Tilt foot 80 includes shaft 81 that protrudes from the bottom surface of the case and foot 82 that contacts installation surface 83 such as the top surface of a table. Shaft 81 passes through opening 86 of locking lever 85 that can slide back and forth, and projection 87 is formed on the inner surface of opening 86. Locking lever 85 is rotatably supported by means of axis of rotation 88, and one end of locking lever 85 is secured to one end of spring 84. The other end of spring 84 is secured to any position of the case.
Accordingly, the restoring force F1 of spring 84 normally presses projection 87 of locking lever 85 against shaft 81, thereby locking shaft 81 (refer to FIG. 2A). However, when a control button (not shown in the figure) is pressed, force F2 acts upon locking lever 85 by way of a release mechanism (not shown in the figure) such that locking lever 85 rotates around axis of rotation 88 as the fulcrum and projection 87 separates from shaft 81 (refer to FIG. 2B). As a result, the locked state of shaft 81 is released, and the length of the extension of shaft 81 can be adjusted. After the length of the extension of shaft 81 has been adjusted to the desired length, the control button is released and locking lever 85 automatically returns to its original position, whereby shaft 81 is again locked.
As described in the foregoing explanation, one control button was provided for one tilt foot in the prior art. In other words, only one foot could be locked or released through the manipulation of one control button. Accordingly, adjusting the lengths of protrusion of two or more tilt feet necessitated the separate manipulation of two or more control buttons, and operability was extremely poor.